Changes for the Chalet School, and the re-read

I've been collecting Elinor M. Brent-Dyer's Chalet School series for 15 or 16 years, and last fall I got the last book I needed in the main collection (she wrote 58 books in the series, and then at least ten connectors. I'm missing at least one of those). So I celebrated - though I think that increasingly, "celebrated" isn't the correct word - this achievement by re-reading them all.
I wish I'd thought to rank the books as I read them! But no time like the present! I finished Changes for the Chalet School a few days ago. I'd guess it would fall around the 40th percentile. It features Bride Bettany and her friends as Head Girl and prefects, which saves it from the bottom third of the percentile. On the other hand, I think this is the book in which Joey jumps the shark as a character. Also, this book marks the departure of Miss Slater - also a favorite character of mine, due to her impatience with Margot Maynard, reminiscences of Old Chaletians, and the assumption that a teacher in a Welsh school would be delighted to teach in German several days a week.
I think the negatives outweigh the positives here.